1. Field of the Invention
This invention relates to pumps and particularly to pumps adapted for pumping sewage and other liquids in which solid matter and stringy material is disposed.
2. Description of Related Art
Certain well known formulas determine the inlet (suction) opening area of sewage pumps. If the inlet opening is too large, the pump uses a larger amount of energy than is desired due to the amount of extra fluid pumped. If the inlet opening is too small, it restricts the amount of fluid that can enter the pump and thus decreases performance. To overcome the pressure drop encountered due to the smaller opening, a larger amount of energy than with a properly sized opening is required to pull the fluid through the opening.
In known prior art pump designs the inlet opening is round and the formula dictates an opening diameter which is larger than the size of solids that the pump can safely pass without clogging. To overcome the problem of attempted passage of solids which are too large in diameter, pump manufacturers commonly place screens in the inlet opening to reduce the size which may pass through the pump. Unfortunately, the material which the pump is attempting to pass often contains so-called stringy material, that is long strands of material of some sort, and this stringy material gets caught on the screen that is often disposed over the pump inlet. This ultimately decreases the opening area to a value that is too small to allow the pump to operate properly.
The prior art pumps that have a screen disposed over the inlet of the pump have not been wholly satisfactory because conventional screens will clog very easily.
It is an object of the invention to limit the passage of large solid material from entering the pump while allowing the passage of relatively stringy material.
Another object of the invention is to provide proper suction area for the pump while controlling particle size that is delivered to the pump.
It is an object of the invention to provide apparatus that may even be retrofitted on some existing pumps.
It is an object of the invention to provide apparatus which is inexpensive to manufacture as well as requires a minimum of labor to install.
Still another object of the invention is to provide a form of the invention that will limit the maximum size to the solid that will enter the pump.
Yet another object of the invention is to provide apparatus that will allow simultaneous passage of two discrete generally spheroidal solids simultaneously.
A further object of the invention is to provide apparatus that will also have an opening area that has an optimized area.